1. Field of the Invention
The present invention relates to a developing device in an image forming apparatus, which forms an image by means of an electro-photography by using electrically charged toners, and especially relates to a developing device capable of re-using the toners by recovering the toners, which have never been used in one cycle of the image formation and have remained on the photosensitive body.
2. Description of the Related Art
There is an image forming apparatus, such as a printer or the like, which forms and records an image onto a record paper by means of a so-called electro-photography by use of a developing device, which is provided with at least a photosensitive drum servicing as a photosensitive body and a developing roller.
For this kind of image forming apparatus, a technique is being developed to recover the toners, which have never been used in one cycle of the image formation and have remained on the photosensitive drum (hereinafter, it is referred to as "remaining toners") and re-use the toners, from a view point of saving the resources.
As one effective method of recovering the remaining toners, there is a method of transporting the remaining toners on the photosensitive drum from the photosensitive drum to the developing roller by use of the rotation of the photosensitive drum itself, so as to recover the remaining toners by the developing roller.
In the image formation by means of the electro-photography, impurities such as fine paper fibers, dusts etc. on the record paper, on which the image is to be formed, often attach onto the photosensitive drum. Thus, the remaining toners in such a condition that the impurities are mixed in the remaining toners are recovered and re-used according to the above mentioned method of recovering the remaining toners, resulting in problems that the inside of the toner box is contaminated by the impurities, the life of the toners is shortened, and that the image cannot be clearly formed when the recovered toners are re-used, due to the impurities.